I've had mixed reactions to the graphic novel adaptations I've read so far of Rick Riordan's books. The Lost Hero was better than some, not as good as my favourite. 

The art is decent, but maybe not quite as gorgeous as I would have liked for one of my favourite series. The plot is great of course, as it's based on a fabulous book, and it's generally told quite well although there were a couple of places where I wondered if a reader who hadn't read the prose novel might be a bit confused (they weren't major plot elements). 

Overall I enjoyed it a fair bit, and while I definitely recommend reading Riordan's novel first, I think this is a fun way to reread the story.